1. Field of the Invention
The present invention relates to a molded-case circuit breaker for direct current (DC), and more particularly, to a molded-case circuit breaker for DC in which a connecting conductor for connecting terminals in the DC circuit breaker is configured as an assembly unit and contained in a terminal receiving portion to improve insulation performance and assemblability and reduce occupied space.
2. Description of the Conventional Art
In general, a molded-case circuit breaker (MCCB) is an electrical device that protects a circuit and a load by automatically interrupting the circuit when there is an electrical overload or short circuit. The circuit breaker typically includes a terminal portion provided on the front and rear and forming a circuit connection, a mechanism divided into a fixed contact and a movable contact and mechanically opening and closing a circuit, a trip portion detecting an over-current or short-circuit current in the circuit and causing the mechanism to trip, and an extinguisher for extinguishing an arc produced when interrupting a fault current.
Such a circuit breaker is generally used for alternating current and may be converted for use in DC applications. In order to convert a circuit breaker for AC to one for DC, in the conventional art, connecting conductors (externally connected conductors) may be added to front and rear terminal portions (or a power side terminal portion and a load side terminal portion) of the existing circuit breaker to configure and use circuits in series.
FIG. 1 depicts a perspective view of a four-pole molded-case circuit breaker for AC according to the conventional art. FIG. 2 depicts a perspective view of a four-pole molded-case circuit breaker for DC according to the conventional art. FIG. 3 is an internal perspective view of the circuit breaker of FIG. 2, from which the cover is partially cut away and the externally connected conductors are separated. FIG. 4 is a perspective view of a trip portion shown in FIG. 3. FIG. 5 is an exploded perspective view of tripping mechanisms, terminals, and an externally connected conductor shown in FIG. 4. FIG. 6 depicts a wiring diagram of the four-pole molded-case circuit breaker for DC according to the conventional art.
As is generally known, a molded-case circuit breaker for AC according to the conventional art includes a switch mechanism 3, a contact portion 7, a trip portion 5, and a terminal portion 2a, 2b, 2c, 2d, 2e, 2f, 2g, and 2h which is placed within an outer casing consisting of a case 1a and a cover 1b. Other internal components than the switch mechanism 3 are provided for each phase. That is, in the four-pole circuit breaker, these components are provided for each of four phases: R phase, S phase, T phase, and N phase. The terminal portion 2a, 2b, 2c, 2d, 2e, 2f, 2g, and 2h includes a front terminal portion 2a, 2b, 2c, and 2d on the front of the circuit breaker and a rear terminal portion 2e, 2f, 2g, and 2h on the rear of the circuit breaker.
In order to use the circuit breaker for DC applications, externally connected conductors 4a and 4b are attached to the rear terminal portion 2e, 2f, 2g, and 2h and the front terminal portion 2a, 2b, 2c, and 2d. FIGS. 2 and 3 show an example of a molded-case circuit breaker for DC to which the externally connected conductors are connected The front terminal portion 2a, 2b, 2c, and 2d has a plurality of U-shaped externally connected conductors that connect two adjacent terminals. In this example, an N phase front terminal 2a and an R phase front terminal 2b are connected by a U-shaped externally connected conductor 4a, and an S phase front terminal 2c and a T phase front terminal 2d are connected by a U-shaped externally connected conductor 4b. In the rear terminal portion 2e, 2f, 2g, and 2h, an I-shaped externally connected conductor 4b may be connected to each phase. In the rear terminal portion 2e, 2f, 2g, and 2h and the front terminal portion 2a, 2b, 2c, and 2d, an insulation barrier 6 may be mounted between each of the externally connected conductors 4a and 4b in order to ensure insulation.
Referring mainly to FIGS. 3 to 5, the trip portion 5 includes a crossbar 5b mounted across a trip portion case 5a, a heater 5d connected to a fixed contact (not shown) of the contact portion 7, bimetal 5c that is bent by heat generated from the heater 5d in case of an over-current in a circuit and that presses a contact region 5b1 of the crossbar 5b to rotate the crossbar 5b, a magnet 5e that has a magnetic force, an armateur 5f that is magnetized in case of a sudden over-current ad rotates in the direction of the magnet 5e, and a trip spring 5g. A tripping mechanism including the heater 5d, bimetal 5c, magnet 5e, amarteur 5f, and trip spring 5g is provided for each phase. Each terminal of the front terminal portion 2a, 2b, 2c, and 2d may be connected to the heater 5d. 
FIG. 5 depicts a pair of tripping mechanisms, a pair of terminals, and a U-shaped externally connected conductor 4a connecting the pair of terminals. The U-shaped externally connected conductor 4a serves to connect two adjacent terminals.
FIG. 6 shows a wiring diagram of the molded-case circuit breaker for DC according to the conventional art. The U-shaped externally connected conductor 4a is attached to the front terminal portion 2a, 2b, 2c, and 2d in such a manner that a pair of adjacent terminals are connected. A load 8 and a power source 9a and 9b are connected to the rear terminal portion 2e, 2f, 2g, and 2h. 
In the DC circuit breaker according to the conventional art, a U-shaped externally connected conductor 4a connecting adjacent terminals is required in order to convert a circuit breaker for AC to one for DC applications. Thus, additional operation is needed, and the externally connected conductor is exposed out of the outer casing of the circuit breaker, thus causing a degradation in insulation performance. Moreover, the presence of the externally connected conductor outside the outer casing of the circuit breaker increases occupied space.